Ball and shot manufacture by impacting process



Sept. 7, 1965 s. R. ECKSTEIN ETAL 3,204,320

BALL AND SHOT MANUFACTURE BY IMPACTING' PROCESS Filed Aug. 29, 1962 2Sheets-Sheet 1 J27 V627 tor-a: George RZ'ciste/h, flame/a LS. Rate,

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United States Patent 3,204,320 BALL AND SHOT MANUFACTURE BY IMPACTINGPROCESS George R. Eckstein, Fairfield, and Donald S. Foote, GreensFarms, Conn., assignors to Remington Arms Company, Inc., Bridgeport,Conn, a corporation of Delaware Filed Aug. 29, 1962, Ser. No. 220,222 12Claims. (Cl. 291.22)

This invention relates in general to an economical method and apparatusfor mechanically producing small, substantially spherical balls fromnon-spherical metal blanks.

In general, there are two classes of methods by which shot or smallmetal balls are mainly produced today: (1) thermal and (2) mechanical.

In the thermal methods of producing shot, various operations areperformed with the metal while the metal is in the molten stage. Themost common method and one which is still in widespread use afterapproximately 180 years is the dropping process. This process consistsof dropping molten lead down a very long shot tower where the fallingmolten lead is broken up into particles and received in a pool of waterat the bottom to solidify the shot.

Although the cost of manufacturing lead shot by this process is low, theprocess is not adaptable for producing shot of different metals, e.g.,iron, aluminum, etc. Iron, for example, has a high melting point andother properties which do not permit economical dropping. In addition,shot towers for the dropping process must be built very high (150180feet) in order to provide enough falling distance in order to producesubstantially spherical shot. These and other limitations have resultedin a widespread search in the past for an economical method of producingshot which would eliminate the very high and expensive tower structureand which is adaptable to produce shot of metals other than of lead.

Other thermal methods of producing shot include: (1) dropping of moltenmetal in an inert atmosphere, or (2) dropping through liquid coolants orsome special materials to change the properties of the metal, or (3)directing a stream of air, water, steam, etc., at molten metal to breakthe metal stream up into small spherical particles. Of course, there areother processes which are not mentioned here.

In the mechanical methods of producing shot, some operation is performedon a solid pellet, slug or blank until the solid particle is rounded offinto substantial sphericity.

It must be appreciated that the problem here is not merely to produceround shot. There are many methods shown in the prior art and in usetoday which will produce very fine, spherical metal balls fromcylindrical or cubical blanks. The problem is to produce very largeamounts of satisfactory metal shot economically. It became apparent fromthe prior art that if the vast daily requirements of shot were to beproduced mechanically at a permissible cost, a new concept of formingshot would be necessary.

The general object of this invention is to produce by novel andmechanical means substantially spherical balls from non-spherical,deformable, metallic pellets.

Another object of this invention is to provide a novel method ofproducing large quantities of shot efliciently and economically.

Another object of this invention is to provide a novel low-cost methodof providing accurately-sized, substantially-spherical shot of anydesired diameter and composition, e.g., lead, steel, aluminum, etc.

Other objects and advantages of the invention will become apparent afterreading the following specification, the claims, and the accompanyingdrawings in which:

FIGURE 1 shows a schematic of the rotating chamber with the impellerassembly inside.

FIGURES 2 and 3 are similar to FIGURE 1 except that the blanks are beinghit at different points on the impeller with resulting differentpatterns.

FIGURE 4 shows a perspective view of a production model encompassing theinvention.

FIGURE 5 shows a cross-sectional view taken on line 44 in FIGURE 4.

FIGURE 6 shows an end view of the discharge end of the drum container ofFIGURE 4.

FIGURE 7 shows a graph showing generally the relationship of impactspeed, impact time and ball roundness.

In the following description of the present invention, reference will bemade to the production of lead shot. It should be appreciated, however,that the process and apparatus is the same for other materials. Asexplained below, the speed of the rotating impeller will vary with thephysical characteristics of the blanks but otherwise the followingdiscussion will also apply to making steel, aluminum and other metallicshot.

The method of the present invention includes the feeding ofnon-spherical lead pellets into a substantially enclosed chamber,projecting the lead pellets into the path of a high-speed impellermounted within the cham ber, striking said pellets with the impeller tocause the pellets to become deformed and subsequently impacted againstthe chamber walls for further impacts and deformation, maintainingsuccessive impacts until the blanks have attained the necessarysphericity :at which time they are removed from the chamber.

The embodiment of FIGURE 1 shows a cylindrical container 10 in whichnon-spherical metallic blanks 12 are placed. The blanks are preferablycylindrical although cubes also will perform satisfactorily. Thecontainer is mounted by means not shown to rotate slowly about itslongitudinal axis 14. Rigidly mounted on the inner wall 16 of thecontainer 10 and rotating therewith are a plurality of scoops 18. As theblanks fall to the bottom of the container by gravity, the scoops 18pick them up and elevate them to approximately the 11 oclock positionshown in FIGURE 1 where the blanks fall by gravity into the centralinterior area of the container.

Centrally positioned within the container 10 to rotate therein atrelatively high speed about the longitudinal center axis 14 of thecontainer is a shaft 20 to which is secured an impeller assembly 22having vanes or blades 24 and 26. Vanes 24 and 26 have rearwardlydirected, streamlined end portions 28 and 30 for a purpose to beexplained later.

As the blanks 12 fall from the scoops 18, they are impinged by theimpeller 22 which is rotating at a predetermined high speed sufficientto deform the blanks to the desired sphericity. In delivering the firstimpact and deformation to the non-spherical blank, the impeller changesboth the direction and magnitude of the velocity of the blank so thatthe blank is projected against the inside wall 16 of the container 10for a second impact and deformation. Then, depending on various factorsmentioned below, the blank either bounces back into the path of theimpeller for another impact (FIGURE 3) or it ricochets and bounces ofi"the inside wall 16 until it is stopped by the scoops 18 (see FIGURES 1and 2).

In a matter of minutes (see FIGURE 6), (depending on the various factorsexplained below), cylindrical or cubical blanks can be deformed andreshaped into substantially spherical balls. Depending on ultimate use,the balls can then be run through a second finishing drum or containerhaving a slower rotating impeller or run through any well-known ballfinishing machine to attain the roundness or sphericity required.

FIGURES 4 and 5 show the inventive concept embodied in a productionmodel adapted to be run as a continuous process but which can also beoperated as a batch process. This embodiment shows an elongatedcylindrical drum 34 supported on spaced rollers 36 and rial under theconditions within the impact drum. Yield strengths for lead and zinc arenot given since they are under creep condition at room temperature.Obviously, the results can be varied by varying any of the following:the diameter of the impeller, the number of impeller vanes; the numberof lifting scoops; and the speed of the rotating drum container.

Yield Impeller Time Percent Original shape and Metal SAE strength,speed, (min.) spher. Dimensions p.s.i. r.p.m.

500 7. 5 Cyl. 0.0160 x 0.137. 250 5. 3 Cyl. 0.160 x 0.137. Lead 500 154. 7 Cyl. 0.160 x 0.137. 500 10 7. 8 Cyl. 0.257 x 0.215. 250 15 5. 7Cyl. 0.257 X 0.215. 500 15 6. 1 Cyl. 0.257 x .0215. 1, 000 5. 9 Cube0.250. 1, 500 10 5. 4 Cube 0.250. Stool 0 6. 5 Cyl. 0.310 x 0.265. 1,500 15 7. 4 Cyl. 0.310 x 0.205. 1, 000 35 4. 5 Cyl. 0.156 x 0.137. 1,500 15 5. 7 Cyl. 0.156 x 0.137. 1, 000 10 6.9 Cyl. 0.0250 x 0.215. 1,500 5 7. 7 Cyl. 0.0250 x 0.215. 1222 i3 -2 2a;- 5. u e Alummum 1, 000 15s. 3 Cyl. 0.250 x 0.215. 1, 500 10 6. 4 Cyl. 0.250 x 0.215. 1, 000 15 4.0 Cyl. 0.250 x 0.215. 1, 500 10 7.] Cyl. 0.250 x 0.215. Zinc 500 35 4. 7Cyl. 0.250 x 0.215. 750 3 10. 1 Cyl. 0.250 x 0.215.

1 Maximum diameter minus minimum diameter/maximum diameter.

38 and rotated slowly by a chain 40 which is connected to a power means(not shown) and which operatively engages a sprocket 42 mounted at oneend 44 of the drum.

Extending through the drum on the longitudinal axis thereof is a shaft46 which is rotatably mounted in bearing blocks 48 and 50. Attached tothe shaft 46 in order to provide rigidity thereto is a spider member 52on which are mounted impeller vanes 54, 56, 58, and 60 having arcuateend portions 540, 56a, 58a, and 60a. The shaft and impeller assembly arerotated independently of the drum by belt 62.

The arcuate end portions of the impeller vanes have been found to benecessary in order to prevent marking of the finished ball which wouldbe caused by any sharp corners of the impacting vanes travelling at highspeed. The degree of curvature of the vane end portions can be varied tocontrol the direction in which the blank is projected after being hit bythe rotating impeller. However, in order to prevent marking of the ballwhen hit by the impeller, the radius of curvature of the rounded vaneend portion must be greater than the maximum radius of ball which is tobeproduced.

A feed hopper 64 is positioned at one end of the drum with a mouthportion 66 extending into the interior of the drum. At the opposite endof the drum, an opening 68 is provided in the drum, end plate 70 forwithdrawing the finished shot from the drum. It can be seen thatnonspherical blanks can be fed continuously to the drum through hopper64 and finished balls withdrawn through opening 68.

It should be appreciated that it is possible to provide more or fewerimpeller vanes as well as scoop elevating means than are shown in thedrawings.

The following results are characteristic of what was achieved byprocessing various samples of metallic blanks with the apparatus shownin FIGURES 1-3 using a 9 inch diameter impeller andwith the drumrotating at 36 rpm. at room temperature. The percent sphericity isarbitrarily defined as maximum diameter minus minimum diameter maximumdiameter The yield strengths are typical values of similar materialtested under static tensile conditions at 0.2% offset and are notnecessarily the actual yield strengths of the mate- It should beappreciated that the above data are not intended to indicate the optimumconditions under which shot can or would be made. For each type ofmaterial, an optimum speed can be determined which will produce asubstantially spherical ball. Obviously, various combinations are alsopossible whereby the initial rounding of the ball can be achieved byrunning the impeller at very high speeds and then running at lowerspeeds for the final rounding off.

Experience has shown certain physical relationships which permit acertain degree of predictability in regards to the forming of metallicshot by the impact process of the present invention. For example, thehigher the yield strength, the higher the impact velocity and timerequired to deform the blanks.

It is known that a higher impact velocity will produce larger fiat areason a metallic blank than a low impact velocity. It is also known (seeFIGURE 7) that a blank impacted at high velocity will reach substantialsphericity sooner than a blank impacted at low velocity. However, theultimate degree of sphericity of the high-velocity produced ball will belower than the low-velocity produced ball.

It was found that certain defects existed in balls formed by the presentmethod which was objectionable for some uses. These defects, leafing andpoling, are caused by the mechanical movement of the metal in beingtransformed from a cylindrical or cubical blank into a rounded ball. Theleafing results in thin laminations of metal on the outer ball peripherywhich can be peeled off much like layers of skin and is believed to becaused by the skidding action of the blanks on the chamber or drumwalls. The poling is caused when angular corners are impacted togetherso that two masses of metal are physically forced together without beingfused together. For a ball formed from a cylindrical blank, two lines orpoles can be seen under a microscope whereas a cubical blank producessix. (Thus, the preference for using cylindrical blanks.) Either ofthese defects may prevent the user of the balls (in some instances)while they obviously are satisfactory for many other uses.

Since it was believed that the skidding action of the blank on the drumwalls was causing the undesirable leafing, various elforts were made toeliminate or at least to lessen the skidding. One effort which wassuccessful in greatly reducing the leafing was the introduction oflubricating oil in the drum so that the blanks would deformed by thedirect impacts of the impeller and the drum but the abrasive action ofthe skidding blanks would be eliminated or substantially decreased.

The poling situation was materially improved by impacting aluminumblanks at elevated temperatures. Since it would be difficult to heat theblanks and maintain them at a constant temperature, the drum orcontainer was heated and kept at approximately 850 F. and the impactingcarried out as previously explained. It was found that the impactingprocess at higher temperatures does not only eliminate the leafing butalso greatly reduces the size of the voids in the pole areas.

The hot-working of the aluminum blanks was found to produce a thin oxidelayer on the surface of the balls, which resulted in a dark color finishinstead of the bright shiny finish produced by the cold impacting.However, if this is found to be undesirable for any reason,'the blankscan be impacted at elevated temperatures in an inert atmosphere in orderto eliminate this discoloration.

Although the heating of the drum is not shown on the drawings, this canbe done by any means well known today. For example, cement kilns andother drums are kept at constant elevated temperatures.

It was found that some blanks, which were made by chopping extruded ordrawn wire into small slugs, were difficult to impact into substantiallyspherical balls. This problem was attributed to the difficulty inreshaping the metal blanks, which had been initially stressed at greaterdegree in the axial direction than in radial or transverse directionduring the wire-forming operation.

This situation was improved, however, by heating the blanks to asufliciently high temperature prior to impacting in order to relieve theintial stresses caused by the wire drawing. The annealing of the blankscan be done prior to cold impacting or hot impacting for improvedresults.

Although the specification shows and explains one experimental model andone production embodiment, it is obvious that the inventive conceptsexpressed herein can be utilized in various other embodiments.

What is claimed is:

1. Apparatus for forming substantially spherical balls fromnon-spherical deformable blanks comprising: an elongated drum mounted torotate at a relatively slow speed on its axial center line, carriermeans rigidly mounted on the inside wall of the drum to move with thedrum and lift the blanks to an elevated position until the blanks fallby gravity into the path of impeller means mounted within said drum androtating at a predetermined relatively high speed, said impeller meansimpinging against and causing the blanks to be thrown against the druminside Wall repeatedly at high speed to cause the non-spherical edges ofthe blanks to be rounded oil.

2. In apparatus for forming balls from angular, deformable blanks, thecombination comprising means to feed the deformable blanks to arelatively slowly rotatable cylindrical container, means within saidcontainer and rotating therewith to elevate the blanks to a point wherethe blanks fall by gravity into the path of impeller means rotating at arelatively high speed within said container whereby said impeller meansimpinges and changes both the direction and magnitude of the velocity ofthe blanks to cause the blanks to undergo a series of impacts againstthe inside wall of the container, and means to draw off the roundedballs.

3. The combination recited in claim 2 wherein said impeller meansincludes radially extending vane means having end portions which arecurved rearwardly, said curved portions having a radius of curvaturegreater than the maximum radius of ball to be produced.

4. Apparatus for mechanically forming shot from nonspherical deformableblanks comprising an elongated,

cylindrical container which revolves at a relatively slow speed on itsaxial center line, scoop means mounted on the inside wall of saidcontainer and adapted to pick up and elevate said blanks from a pointnear the lower end of a circle formed by the revolving container to apoint near the top of the circle where the blanks fall by gravity intothe interior of the container, and impeller means rotatable within saidcontainer on said axial center line of said container at a predeterminedrelatively high speed to strike the blanks and change both the directionand magnitude of the velocity of said blanks and cause the blanks to beimpacted at high velocities against the inside container wall and becomerounded off.

5. Apparatus as recited in claim 4 wherein means are provided to heatthe rotating container and the blanks therein to an elevated temperaturegreater than normal room temperature but less than the melting point ofthe metal blanks.

6. An apparatus for mechanically rounding off nonspherical deformableparticles comprising a substantially enclosed chamber having an inletwhereby non-spherical particles are continuously fed into said chamberand an outlet whereby rounded balls are continuously withdrawn,elevating means within said chamber to continuously pick up, elevate anddischarge said particles into the path of a continuously-rotating,high-speed vane assembly which throws the particles against the insidechamber wall, thus rounding ofii said non-spherical particles andresulting in substantially spherical balls.

7. The apparatus recited in claim 6 wherein means are provided tomaintain the blanks at an elevated temperature above room temperaturebut below the melting point of the blanks while being impacted.

8. In an apparatus for mechanically forming shot by impactingnon-spherical blanks in order to produce rounded balls, the combinationof a rotatable cylinder container, means to elevate and recirculate theblanks within said container, and rotatable impact means within saidcontainer to change the direction and provide a velocity of sufficientmagnitude thereto to deform the blanks upon being impacted against thecontainer inner wall.

9. The combination recited in claim 8 wherein said elevating meanscomprises at least one scoop attached to the inner container wall topick up, lift and discharge by gravity the blanks into the interior ofsaid container whereby said impact means strikes the blanks and changesboth the direction and magnitude of the velocity thereof.

10. The combination recited in claim 9 wherein said means within thecontainer to change both the direction and magnitude of the velocity ofthe blanks comprises a vane assembly which rotates at high speed on thesame axis as the rotating container.

11. The combination recited in claim 10 wherein said rotatable vanemeans includes a curved end portion which is swept back opposite to thedirection of vane rotation in order to prevent marking of the finishedball.

12. The combination recited in claim 9 wherein said drum rotates at arelatively slow speed and said elevating means comprises scoop meansmounted on said rotatable drum.

References Cited by the Examiner UNITED STATES PATENTS 1,601,252 9/26Lines. 2,758,360 8/56 Shetler 291.22 2,815,560 12/57 Buxton 29-l.222,946,115 7/60 Firm.

FOREIGN PATENTS 13,537 6/11 Great Britain. 75,373 7/49 Norway.

OTHER REFERENCES Finishing Springs by Shot Peening, Machinery, June 18,1954, p. 1300.

RICHARD H. EANES, JR., Primary Examiner.

1. APPARATUS FOR FORMING SUBSTANTIALLY SPHERICAL BALLS FROMNON-SPHERICAL DEFORMABLE BLANKS COMPRISING: AN ELONGATED DRUM MOUNTED TOROTATE AT A RELATIVELY SLOW SPEED ON ITS AXIAL CENTER LINE, CARRIERMEANS RIGIDLY MOUNTED ON THE INSIDE WALL OF THE DRUM TO MOVE WITH THEDRUM AND LIFT THE BLANKS TO AN ELEVATED POSITION UNTIL THE BLANKS FALLBY GRAVITY INTO THE PATH OF IMPELLER MEANS MOUNTED WITHIN SAID DRUM ANDROTATING AT A PREDETERMINED RELATIVELY HIGH SPEED, SAID IMPELLER MEANSIMPINGING AGAINST AND CAUSING THE BLANKS TO BE THROWN AGAINST THE DRUMINSIDE WALL REPEATEDLY AT HIGH SPEED TO CAUSE THE NON-SPHERICAL EDGE OFTHE BLANKS TO BE ROUNDED OFF.